In a mobile communication system in which space division multiplex communication is performed, the reception powers of signals received from a plurality of space-division multiplexed mobile station apparatuses by a base station apparatus need to be equalized to some extent. In order to realize this, in the related art, a remaining power value of transmission power (a value obtained by subtracting the present transmission power from the maximum transmission power) is transmitted from a mobile station apparatus to a base station apparatus. The base station apparatus performs processing described below on the basis of the remaining power value received from each mobile station apparatus so that the reception powers are equalized.
More specifically, on the basis of the remaining power value received from each mobile station apparatus, first, the base station apparatus selects a mobile station apparatus having the smallest reception power when transmission is performed at the maximum possible transmission power. The mobile station apparatus is usually a mobile station apparatus (mobile station apparatus in which the path of radio waves is longest) at a position farthest from the base station apparatus among the mobile station apparatuses and therefore, will be hereinafter referred to as the “farthest mobile station apparatus”. Next, the base station apparatus maximizes the transmission power of the farthest mobile station apparatus. Finally, the base station apparatus adjusts the transmission powers of the mobile station apparatuses other than the farthest mobile station apparatus so that the reception powers of the signals received from the mobile station apparatuses other than the farthest mobile station apparatus are equalized.
Japanese Unexamined Patent Application Publication No. 2005-6089 discloses a technology related to determination of transmission power of a base station apparatus in accordance with a modulation method used for communication by mobile station apparatuses during space division multiplex communication.